With the development of increasingly sophisticated technology, pumps have been created which have demonstrated the feasibility of substituting a pump for the human heart for either temporary purposes such as during an operation or while awaiting a heart transplant or for permanent employment as a substitute for the human heart. A great variety of different types of pumps have been developed to effect these objectives. In most instances depending upon the type of actuation employed, the pump design results in a compromise of various features making it desirable for some aspects of these applications but undesirable for other aspects. Characteristics which are material in this respect include the number of moving parts, the complexity of the pump, the size of the pump, the power requirements, the extent of necessary controls and the overall reliability of the pump components.
Some of the types of pumps which have been developed for use in such a medical environment or for comparable purposes are summarized hereinafter. A common type of pump involves a floating piston movable along the length of a chamber as by a solenoid or mechanical actuation to pump fluid into and out of opposite ends of the chamber through suitable inlets and outlets. Another type of pump which has gained substantial attention involves configurations having pumping chambers of a flexible material. In some instances electrical actuation such as by a plurality of solenoids is employed to controllably distort tubes and thus sequentially displace fluid therefrom. In other instances membranes may be displaced by mechanical devices such as rotors having blades which may be rotated to alternately pump fluid into and out of a housing. Various types of rotor configurations have been employed having differing numbers of chambers which may operate via mechanical drive elements to effect a desired pumping action.
Another type of diaphragm pump which has been employed involves a piston mounting diaphragms at either end with the piston being movable axially so that the chambers formed proximate either end thereof may be increased and reduced in size alternately to effect a desired pumping action. In other instances, diaphragms dividing compartments have been provided with magnetic particles which interact with electromagnets formed in the pump housing to provide controlled displacement of the diaphragm to effect a desired input and output through suitably positioned ports. In other instances efforts have been made to effectively duplicate the actual configuration of a human heart by providing flexible membranes mounting permanent magnets which interact with electromagnets positioned in a housing thereabout to effect alternate repulsion and attraction to achieve a heart-like expansion and contraction of the chambers formed by the membranes for the pumping action.
In many instances the size of the mechanical, electrical, or mechanical and electrical components is of such a magnitude that implantation of the pump as a replacement for the human heart is impossible due to size considerations. In other instances the mechanical configuration necessary, for example, to move a piston or the electrical powering and operation of a motor or rotor makes a device undesirable for implantation or long term usage due to the fact that the number of operating components and the interactions are of such complexity as to render improbable a long term reliable operation of the pump. In some instances fluids have been employed to either actuate or control the movement of a diaphragm; however, in some of these instances it is necessary that the fluid be vented to the atmosphere thereby rendering such devices undesirable for human implant or other environmentally isolated installations. In other instances, pumps may generate sufficient vibration, noise, or heat as to limit their applicability for certain of these uses. Thus, virtually all pumping devices of this nature which have been developed to date suffer from one or more disadvantages or limitations which restrict the type or extent of their usage in environments of this nature.